1. Field of the Invention
The present invention relates to a liquid discharging method for discharging a desired liquid by creating air bubbles by means of thermal energy applied to the liquid, a liquid discharge head, a liquid discharge head cartridge using such liquid discharge head, and a liquid discharge apparatus.
More particularly, the invention relates to a liquid discharge head having a movable member that can be displaced by the utilization of the creation of air bubbles, a liquid supplying method, a head cartridge using such liquid discharge head, and a liquid discharge apparatus.
Also, the present invention is applicable to a printer that records on a recording medium, such as paper, thread, fiber, cloth, leather, metal, plastic, glass, wood, or ceramic, as well as to a copying machine, a facsimile equipment provided with communication systems, a word processor provided with a printing unit, among some others. The invention is further applicable to a complex recording apparatus for the industrial use, which is combined with various processing systems.
2. Related Background Art
There has been known the so-called bubble jet recording method, which is an ink jet recording method whereby to form images on a recording medium by discharging ink from discharge ports using acting force exerted by the change of states of ink brought about by the abrupt voluminal changes (creation of air bubbles) when thermal energy or the like is applied to ink in accordance with recording signals. For the recording apparatus that uses the bubble jet recording method, it is generally practiced to provide, as disclosed in the specifications of U.S. Pat. No. 4,723,129 and others, the discharge ports that discharge ink, the ink paths conductively connected to the discharge ports, and electrothermal transducing elements arranged in each of the ink paths as means for generating energy for discharging ink. Then, it is generally practiced for the bubble jet recording method that the air bubbles are developed by means of film boiling generated in liquid.
In accordance with such recording method, it is possible to record high quality images at high speeds with a lesser amount of noises. At the same time, the head that executes this recording method makes it possible to arrange the discharge ports for discharging ink in high density, with the advantage, among many others, that images are recordable in high resolution, and that color images are easily obtainable by use of a smaller apparatus. In recent years, therefore, the bubble jet recording method is widely adopted for many kinds of office equipment, such as a printer, a copying machine, a facsimile equipment, and further utilized for industrial systems, such as a textile printing, among others.
Along the wider utilization of bubble jet technologies and techniques for various products in many different fields, there have been increasingly more demands technically in recent years as given below.
For example, as to the demand on the improvement of energy efficiency, the adjustment of the thickness of protection film has been studied to optimize the performance of heat generating elements. A study of the kind has produced effects on the enhancement of efficiency of generated heat transferred to ink or other liquids. Also, in order to obtain high quality images, there has been proposed a driving condition under which a liquid discharging method or the like is arranged to be able to execute good ink discharge at higher ink discharging speeds with more stabilized creation of air bubbles. Also, from the viewpoint of a high-speed recording, there has been proposed the improved configuration of liquid flow paths that makes it possible to obtain a liquid discharge head capable of refilling liquid to the liquid flow paths at higher speeds after discharging.
Of the various configurations of liquid flow paths thus proposed, those represented in FIGS. 1A and 1B are disclosed in the specification of Japanese Patent Application Laid-Open No. 63-199972 as a liquid flow path structure. The liquid flow path structure and a method for manufacturing heads disclosed in the specification thereof are the inventions devised with attention to the back waves (the pressure orientated opposite to the direction toward the discharge ports, that is, pressure exerted in the direction toward the liquid chamber 12). The back waves are known as energy loss because such energy is not exerted in the discharging direction.
For the liquid flow path configuration represented in FIGS. 1A and 1B, each of the heat generating elements 2 is provided on an elemental substrate 1. At the same time, each of the valves 90 is arranged in a position opposite to the side where each heat generating element 2 is formed, which is away from the region where the air bubble is created by means of the heat generating element 2. The valve 90 keeps an initial position as if it adheres to the ceiling of the liquid flow path 10 as shown in FIG. 1B by a method of manufacture that utilizes a board material or the like, and then, hangs down into the liquid flow path 10 as an air bubble is being created. In accordance with the invention shown in conjunction with FIGS. 1A and 1B, the back waves described above are partly controlled by use of the valve 90, thus suppressing the progress of the back waves toward the upstream side with the intention to reduce the energy loss. However, as clear from the precise studies on the process in which each of the air bubbles is created, suppressing the back waves partly by the provision of the valve 90 in the interior of the liquid flow path that holds discharging liquid is not practicable with respect to discharging. In other words, the back waves themselves are not directly concerned with discharging fundamentally in this system. As shown in FIG. 1A, the moment the back waves are generated in the liquid flow path 10, the pressure exerted by means of the air bubble that directly concerned with discharging has already acted upon liquid to be discharged from the liquid flow path 10. Therefore, even if the back waves are totally suppressed, it is obvious that a suppression of the kind does not affect discharging greatly, not to mention its partial suppression.
Meanwhile, as to the bubble jet recording method, the heat generating elements repeat heating while the elements are kept in contact with ink. Therefore, sedimentary deposit is made on the surface of each element due to burning of ink. Depending on the kinds of ink, such sedimentary deposit is often produced to make the creation of air bubbles instable, leading to the difficulty in discharging ink in good condition. Also, it has been desired to provide a good method whereby to discharge liquid without changing its quality even when such liquid is the one that easily deteriorates by the application of heat or the one that does not easily provide a sufficient foaming.
From these points of view, it has been proposed and disclosed in the specifications of Japanese Patent Application Laid-Open No. 61-69467, Japanese Patent Application Laid-Open No. 55-81172, and U.S. Pat. No. 4,480,259 that the liquid (foaming liquid) that creates air bubbles by means of heat and the liquid (discharging liquid) that can be discharged are prepared as separate liquids, and then, the discharging liquid is discharged by the transfer of pressure exerted by foaming to the discharging liquid. In these specifications, the structure is arranged so that ink serving as the discharging liquid and the foaming liquid are completely separated by means of a flexible film such as silicon rubber, and at the same time, the foaming pressure of the foaming liquid is transferred to the discharging liquid by the deformation of such flexible film, while the discharging liquid is prevented from being directly in contact with the heating elements. With a structure of the kind, it is made possible to prevent sedimentary deposit on the surface of the heat generating elements, and also, contribute to widening the selection range of discharging liquids.
However, as to the head thus structured to separate the discharging liquid and foaming liquid completely, the arrangement is made so that the foaming pressure is transferred to the discharging liquid by means of deformation effectuated by the expansion and contraction of the flexible film. Therefore, the foaming pressure tends to be absorbed by the flexible film to a considerable extent. Also, the degree of deformation cannot be made sufficiently large for the flexible film. As a result, although it is possible to obtain an effect to separate the discharging liquid and foaming liquid, there is a fear that energy efficiency and discharging force are inevitably lowered.
Now, when air bubbles are created in liquid by heating it using electrothermal transduing elements or the like, there is a possibility that electrothermal transducing elements are damaged due to cavitation brought about at the time of defoaming following the contraction of each of the created air bubbles. To counteract this, it is generally practiced that an anti-cavitation layer formed by tantalum or the like is provided for the surface including the electrothermal transducing elements of a liquid discharge head of the kind. In order to enhance the reliability more, it is also important to consider means for preventing such cavitation more effectively.